This invention relates to a track counting circuit for an optical disk driver having a high speed searching algorithm for finding a track, which precisely counts the intended track and thereby enables easy searching of the track by using an up/down counter.
In a conventional optical disk driver, the intended track is found by using a tracking counter which counts the number of data tracks one by one. However, the mass of the optical pickup frequently results in the pick-up travelling beyond the intended track because of inertial force and eccentricity. Thus, the optical pickup must be moved backwards. Because the tracking counter continues to count the number upwards regardless of the optical pickup moving forwards or backwards, in finding the intended track the tracking counter needs to be reloaded or the track identifying numbers recorded on the optical disk are identified one by one to find the intended track. Accordingly it becomes very difficult to find the intended data track with high speed and there occurs a problem because the algorithm for searching with high speed is complicated. Generally, the high speed searching algorithm to find a track by using the push-pull tracking servo-mechanism involves tracking error signals in order to count up to the intended track, wherein the tracking error signals are obtained, as shown in FIGS. 1A, 1B and 1C depending on the relative position of the beam reflected from the track. Namely, the track is counted by using the tracking error signals, which are employed in the high searching algorithm.
In other words, as shown in FIG. 2, the intended track is set by a microcomputer, by which the track is compared with the track count, and if the intended track is not reached, the microcomputer causes a stepping motor to keep on running. However, since the optical pickup has mass causing inertia, it can not stop at the exact track and frequently goes beyond the intended track. Hence, the optical pickup must be moved backwards, which consequently increases the track count, so that the precise track count is hardly maintained. Namely, the track count is always increased regardless of the optical pickup moving forwards or backwards.
Consequently, in order to find the intended track, the microcomputer resets the intended track buffer or the track identifying numbers recorded on the optical disk are identified one by one to find the intended track, so that it is very difficult to find the intended data track at high speed and there occurs a conflict with the algorithm for exploring at high speed.